Wasson's alternative candidates for soma.

Citing recently published challenges to R. Gordon Wasson's identification of Vedic soma as the psychoactive mushroom Amanita muscaria (fly-agaric), this article reviews unpublished letters by Wasson in which he considered and rejected other psychoactive plants as candidates, including the mint Lagochilus inebrians, Convolvulaceae (morning glory) seeds, the fungal parasite Claviceps purpurea (ergot), and especially the psilocybin mushroom Stropharia cubensis, known also as Psilocybe cubensis. Apart from their historical interest, these letters--from the Tina and Gordon Wasson Ethnomycological Collection at the Harvard Botanical Museum--demonstrate that Wasson remained open to refinements of his theory.